unique-constraint

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how can i set up a uniqueness constraint in mysql for columns that can be null?

I know that in MySQL, UNIQUE constraits don\'t treat NULL values as equal.So if I have a unique constraint on ColumnX, then two separate rows 开发者_开发知识库can have values of NULL for ColumnX and t[详细]

2022-12-24 01:11 分类：问答
Finding ghost constraint from Oracle DB

I had a constraint in a table CREATE TABLE \"USERSAPPLICATIONS\" ( \"USERID\" NUMBER NOT NULL , \"APPLICATIONNAME\" VARCHAR2 (30) NOT NULL ,[详细]

2022-12-21 16:23 分类：问答
A Queue that ensure uniqueness of the elements?

I\'m looking for a implementation of java.util.Queue or something in the Google collection who behave like a Queue, but also ensure that each element of the queue is unique. (all further inse开发者_运[详细]

2022-12-21 04:16 分类：问答
Adding text to a field to make it unique

I am using SQL Server 2000, I have a situation where I am copying data over from one table to another, the destination data table requires ea开发者_如何学运维ch Name row to be unique. Here is a quick[详细]

2022-12-20 18:31 分类：问答
Getting ORA-00001(unique constraint violated) when COMMITing?

We\'re getting a ORA-00001 (unique constraint violated) in a batch job. However, the error occurs when a COMMIT is issued, not at the time the offending record is inserted.[详细]

2022-12-19 06:16 分类：问答
MySQL: Table structure for a user's "views"

I\'ve got a questi开发者_JAVA技巧on to which I\'ve had opposing pieces of advice, would appreciate additional views.[详细]

2022-12-15 19:44 分类：问答
Varchar with trailing spaces as a Primary Key in SQL Server 2008

Is it possible to have a varchar col开发者_StackOverflow中文版umn as a primary key with values like \'a \' and \'a\', is gives always this error \"Violation of PRIMARY KEY constraint\" in MS SQL Serve[详细]

2022-12-14 22:36 分类：问答
Unique constraint on multiple columns

I am using an oracle table and have cr开发者_运维知识库eated a unique constraint over four columns. Can these columns within the constraint have NULL in them?you can have NULLs in your columns unless[详细]

2022-12-13 00:20 分类：问答
How to delete duplicate entries?

I have to add a unique constraint to an existing table. This is fine except that the table has millions of rows already, and many of the rows violate the unique constraint I need to add.[详细]

2022-12-11 20:39 分类：问答
How to make "No Duplicates" column in SQL Server 2008?

I have a simple table in my SQL Server database. This table contains two columns: ID int, Name nvarchar(50). The ID column is the primary key for my table.[详细]

2022-12-08 17:26 分类：问答